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Page
240 (T-H3J), 340 (T-H3S) and 540 (T-H3) models Service Manial
Ver. 1.00
CONFIDENTIAL
12-5. AFR rod function
<Function>
The AFR rod checks flame conditions during combustion. When the AFR rod detects unexpected flame
conditions, the computer board of the water heater adjusts the fan motor speed to ensure that air and
fuel are always at a proper mixture ratio, minimizing emissions.
<The relationship between the AFR stage and the “101” and “991” error codes>
(Condition of AFR stage)
• 0 to 5: Air-rich
• In order to solve the “air excess” problem, the
fan motor speed is automatically decreased
and AFR combustion stage goes down.
• 6: Default
• 7 to 16: Gas-rich or Air shortage
• In order to solve the “air deficiency”
problem, the fan motor speed is
automatically increased and AFR
combustion stage goes up.
• 15: “101” error code
• 16: “991” error code
• When the “101” or “991” error code appears,
see section 12-4.
16
15
6
0
Default condition
"101" error code
"991" error code
Stage
FM
+ 15 %
+ 13.5 %
0 %
- 9 %
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< AFR normal range of values >
• If the detected AFR value is higher than the normal value, the FM speed is increased.
• If the AFR value is lower than the normal value, the FM speed is decreased.
•
These values are read with the front cover close
.
• Measure the values after the water heater for ten minutes.
*The AFR stage can be confirmed in “Diagnostic Mode”. (Section 12-1)
240 (T-H3J) models
Installation type
Direct vent
Outdoor
Gas type
Propane
Natural gas
Propane
Natural gas
Combustion
mode
MAX
12.0 to 35.0 23.6 to 58.0 6.0 to 41.0 17.1 to 55.0
MIN
5.0 to 20.0
3.5 to 11.0
3.0 to 15.0
3.8 to 19.0
340 (T-H3J) models
Installation type
Direct vent
Outdoor
Gas type
Propane
Natural gas
Propane
Natural gas
Combustion
mode
MAX
19.0 to 52.0 24.6 to 65.0 7.0 to 47.0 21.4 to 56.0
MIN
5.0 to 20.0
3.5 to 11.0
3.0 to 15.0
3.8 to 19.0
540 (T-H3) models
Installation type
Direct vent
Outdoor
Gas type
Propane
Natural gas
Propane
Natural gas
Combustion
mode
MAX
20.0 to 57.0 26.2 to 78.0 7.0 to 48.0 22.3 to 60.0
MIN
5.0 to 20.0
3.5 to 11.0
3.0 to 15.0
3.8 to 19.0